2001 C5 part time idle problem
Thread Starter
8th Gear
Joined: Feb 2017
Posts: 8
Likes: 0
2001 C5 part time idle problem
Hello CF members,
Your help is much needed as I'm at a loss right now. I have recently purchased a 2001 coupe with 42,000 miles. Car ran great for about 1 month and then all of the sudden I started getting a bad stumble in gear at a stop. Only at a stop or in park at idle. It will come and go and have researched forums til im blue. No lights or codes have came up. I first changed the MAF sensor and though I solved it and bam, back again. Changed all 4 O2 sensors and nothing. Came across a article about oil in the intake which I did verify that I have that problem. Removed the TB and did a good cleaning and symptom went away. 2 days later back again. Order a 140 oil catch can which I installed and still getting oil in the intake. I need some ideas here as im about ready to change plugs and wires as I have read issues regarding plug wires arching. Before I do i was hoping for some suggestions. Borla exhaust and the passenger side tail pipes have a lot of soot and barely any on the drivers side thus my reason for changing O2 sensors. I'm thinking the oil in the intake is the main issue but not sure where im still getting oil in the intake from. Any good ideas would be appreciated.
Your help is much needed as I'm at a loss right now. I have recently purchased a 2001 coupe with 42,000 miles. Car ran great for about 1 month and then all of the sudden I started getting a bad stumble in gear at a stop. Only at a stop or in park at idle. It will come and go and have researched forums til im blue. No lights or codes have came up. I first changed the MAF sensor and though I solved it and bam, back again. Changed all 4 O2 sensors and nothing. Came across a article about oil in the intake which I did verify that I have that problem. Removed the TB and did a good cleaning and symptom went away. 2 days later back again. Order a 140 oil catch can which I installed and still getting oil in the intake. I need some ideas here as im about ready to change plugs and wires as I have read issues regarding plug wires arching. Before I do i was hoping for some suggestions. Borla exhaust and the passenger side tail pipes have a lot of soot and barely any on the drivers side thus my reason for changing O2 sensors. I'm thinking the oil in the intake is the main issue but not sure where im still getting oil in the intake from. Any good ideas would be appreciated.
Burning Brakes
Joined: Jul 2011
Posts: 996
Likes: 306
From: Southern Norway , Europe
Maybe you have a vacuumleak somewhere in the intake or attached lines lines .
If the engine is getting extra (false) air not detected by the MAF it will
cause lean conditions at the O2 sensors . Then the ECM will add more fuel
to correct this . The fueltrim values will reflect this if you connect a scanner or a Tech 2 .
The vaccumports is on the rear side of the intake and goes to the MAP sensor , brakebooster and to the climate system and the air system . Please see this post for more photoes of theese lines
https://www.corvetteforum.com/forums...nge-vents.html
Check also if you a leak on the EVAP purge solonoid line located on the driver side head .
If the engine is getting extra (false) air not detected by the MAF it will
cause lean conditions at the O2 sensors . Then the ECM will add more fuel
to correct this . The fueltrim values will reflect this if you connect a scanner or a Tech 2 .
The vaccumports is on the rear side of the intake and goes to the MAP sensor , brakebooster and to the climate system and the air system . Please see this post for more photoes of theese lines
https://www.corvetteforum.com/forums...nge-vents.html
Check also if you a leak on the EVAP purge solonoid line located on the driver side head .
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
WELL,,,,,,, 
The easiest route would have been to start at the plugs and wires.
If it were me, I would order some GM Performance Red Wires & OEM AC Delco plugs and install them.
Make sure that you use a small bit of antiseize on the plug threads and use dielectric grease on the plug boots to prevent them from sticking to the plugs and coil towers.
NO LIGHTS or CODES.... How are you reading the DTCs????? Are you using the DIC??
What lights? If you have a valid MISFIRE, it can and will cause the Check Engine Light to FLASH when the PCM is actually detecting the misfire condition.
DATA LOG THE PCM. You can use the DIC to read ALL the C5 DTC but you have to have a scanner that can read and displat LIVE SENSOR DATA to see what is really going on.
I recommend investing in a hand held scanner that has the ability to read all your Live Sensor Data and check LTFT, O2 Sensor data, etc......
BC
The easiest route would have been to start at the plugs and wires. If it were me, I would order some GM Performance Red Wires & OEM AC Delco plugs and install them.
Make sure that you use a small bit of antiseize on the plug threads and use dielectric grease on the plug boots to prevent them from sticking to the plugs and coil towers.
NO LIGHTS or CODES.... How are you reading the DTCs????? Are you using the DIC??
What lights? If you have a valid MISFIRE, it can and will cause the Check Engine Light to FLASH when the PCM is actually detecting the misfire condition.
DATA LOG THE PCM. You can use the DIC to read ALL the C5 DTC but you have to have a scanner that can read and displat LIVE SENSOR DATA to see what is really going on.
I recommend investing in a hand held scanner that has the ability to read all your Live Sensor Data and check LTFT, O2 Sensor data, etc......
BC
Thread Starter
8th Gear
Joined: Feb 2017
Posts: 8
Likes: 0
Maybe you have a vacuumleak somewhere in the intake or attached lines lines .
If the engine is getting extra (false) air not detected by the MAF it will
cause lean conditions at the O2 sensors . Then the ECM will add more fuel
to correct this . The fueltrim values will reflect this if you connect a scanner or a Tech 2 .
The vaccumports is on the rear side of the intake and goes to the MAP sensor , brakebooster and to the climate system and the air system . Please see this post for more photoes of theese lines
https://www.corvetteforum.com/forums...nge-vents.html
Check also if you a leak on the EVAP purge solonoid line located on the driver side head .
If the engine is getting extra (false) air not detected by the MAF it will
cause lean conditions at the O2 sensors . Then the ECM will add more fuel
to correct this . The fueltrim values will reflect this if you connect a scanner or a Tech 2 .
The vaccumports is on the rear side of the intake and goes to the MAP sensor , brakebooster and to the climate system and the air system . Please see this post for more photoes of theese lines
https://www.corvetteforum.com/forums...nge-vents.html
Check also if you a leak on the EVAP purge solonoid line located on the driver side head .
Checked for vacuum leaks and nothing. I would assume the vacuum leak would give me issues all the time.
Thread Starter
8th Gear
Joined: Feb 2017
Posts: 8
Likes: 0
Bill Curlee,
That's what I plan on next as it wont hurt to have new plugs and wires anyways. When this has happened I have checked the onboard DTC and hooked a scanner up which did not reveal any codes. No check engine light flash or anything and that is what has stumped me. What I have done today was disconnected the PCV line from the intake that comes from the catch can and routed the line down towards the ground. I capped of the fitting on the tb and then removed the tb and cleaned any oil that was collected. I have assembled back together and no issue as this morning on the way to work. If it comes back I will hook the scanner up and check what you said but I have replaced all 4 sensors and still does the same.
That's what I plan on next as it wont hurt to have new plugs and wires anyways. When this has happened I have checked the onboard DTC and hooked a scanner up which did not reveal any codes. No check engine light flash or anything and that is what has stumped me. What I have done today was disconnected the PCV line from the intake that comes from the catch can and routed the line down towards the ground. I capped of the fitting on the tb and then removed the tb and cleaned any oil that was collected. I have assembled back together and no issue as this morning on the way to work. If it comes back I will hook the scanner up and check what you said but I have replaced all 4 sensors and still does the same.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Hello CF members,
Your help is much needed as I'm at a loss right now. I have recently purchased a 2001 coupe with 42,000 miles. Car ran great for about 1 month and then all of the sudden I started getting a bad stumble in gear at a stop. Only at a stop or in park at idle. It will come and go and have researched forums til im blue. No lights or codes have came up. I first changed the MAF sensor and though I solved it and bam, back again. Changed all 4 O2 sensors and nothing. Came across a article about oil in the intake which I did verify that I have that problem. Removed the TB and did a good cleaning and symptom went away. 2 days later back again. Order a 140 oil catch can which I installed and still getting oil in the intake. I need some ideas here as im about ready to change plugs and wires as I have read issues regarding plug wires arching. Before I do i was hoping for some suggestions. Borla exhaust and the passenger side tail pipes have a lot of soot and barely any on the drivers side thus my reason for changing O2 sensors. I'm thinking the oil in the intake is the main issue but not sure where im still getting oil in the intake from. Any good ideas would be appreciated.
Your help is much needed as I'm at a loss right now. I have recently purchased a 2001 coupe with 42,000 miles. Car ran great for about 1 month and then all of the sudden I started getting a bad stumble in gear at a stop. Only at a stop or in park at idle. It will come and go and have researched forums til im blue. No lights or codes have came up. I first changed the MAF sensor and though I solved it and bam, back again. Changed all 4 O2 sensors and nothing. Came across a article about oil in the intake which I did verify that I have that problem. Removed the TB and did a good cleaning and symptom went away. 2 days later back again. Order a 140 oil catch can which I installed and still getting oil in the intake. I need some ideas here as im about ready to change plugs and wires as I have read issues regarding plug wires arching. Before I do i was hoping for some suggestions. Borla exhaust and the passenger side tail pipes have a lot of soot and barely any on the drivers side thus my reason for changing O2 sensors. I'm thinking the oil in the intake is the main issue but not sure where im still getting oil in the intake from. Any good ideas would be appreciated.
Lets address some of your concerns:
See my comments in blue
Your help is much needed as I'm at a loss right now. I have recently purchased a 2001 coupe with 42,000 miles. Car ran great for about 1 month and then all of the sudden I started getting a bad stumble in gear at a stop. Only at a stop or in park at idle. It will come and go and have researched forums til im blue. No lights or codes have came up. I first changed the MAF sensor and though I solved it and bam, back again. Changed all 4 O2 sensors and nothing.
ONLY the 2 Primary O2 sensors have ANYTHING to do with engine management. The post CAT sensors are only there to monitor nd report emissions and cat status.
Its possible that the new O2 sensors are still NOT performing correctly. The scanner will tell you that.
Came across a article about oil in the intake which I did verify that I have that problem. Removed the TB and did a good cleaning and symptom went away. 2 days later back again. Order a 140 oil catch can which I installed and still getting oil in the intake.
ALL C5s have oil in the intakes. Yes a Catch can will help. Are you POSITIVE that ALL of your PCV pluming is sound and not broken (very common issue). Check the ability of ALL of the PCV tubing and fittings ability to hold vacuum The fittings behind the manifold are well known to crack and rot!!
I need some ideas here as im about ready to change plugs and wires as I have read issues regarding plug wires arching. Before I do i was hoping for some suggestions. Borla exhaust and the passenger side tail pipes have a lot of soot and barely any on the drivers side thus my reason for changing O2 sensors.
Oil in the intake would effect BOTH banks. Its not bank selective. SOOTY one bank tells me that you have a BANK issue. Coil Packs, injetors etc.. There are two coil power bank fuses. They are IGNITION SWITCH POWERED. See what the voltage is on the fuse test slots on top of the fuse to chassis ground (ignition switch to ON) Should be full battery voltage.
On the back of the drivers cyl head is the coil pack ground. Check that ground and the two ground wires in the EYELET.
I'm thinking the oil in the intake is the main issue but not sure where im still getting oil in the intake from. Any good ideas would be appreciated.[/QUOTE]
IMHO, Oil in the intake is your least worries.
What does the IPC Volt meter on the IPC read when the engine acts up? You can also see that voltage in the DIC if you pull it up to monitor it.
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Thread Starter
8th Gear
Joined: Feb 2017
Posts: 8
Likes: 0
Hello Bill,
A lot of great info. Sorry for the late response. I will check these tomorrow in the morning and respond. As foe the IPC it doesnt do anything when this happens and I have no IPC codes new or old. I will check the PCV line but im not sure how that would make it run bad as the line is simply a outlet for fumes. Both ends have a pcv valve on them which utilizes a one way check valve correct? I'm kinda starting to think your on the money with the passenger side bank issue. Today I ran with the pcv line disconnected from the TB and no change as it still stumbled for about 3 seconds. Just to clarify, No codes or check engine lights when this happens. As rough as it stumbles you would think some kind of fault code would appear. I did check the DIC onboard and the RDO brought up to history codes. u1000 and u1064
A lot of great info. Sorry for the late response. I will check these tomorrow in the morning and respond. As foe the IPC it doesnt do anything when this happens and I have no IPC codes new or old. I will check the PCV line but im not sure how that would make it run bad as the line is simply a outlet for fumes. Both ends have a pcv valve on them which utilizes a one way check valve correct? I'm kinda starting to think your on the money with the passenger side bank issue. Today I ran with the pcv line disconnected from the TB and no change as it still stumbled for about 3 seconds. Just to clarify, No codes or check engine lights when this happens. As rough as it stumbles you would think some kind of fault code would appear. I did check the DIC onboard and the RDO brought up to history codes. u1000 and u1064
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Your engine tune is calibrated for that PCV system bypassing a metered amount of air around the throttle blade.
So, when you have a vacuum leak or the PCV leaks or you just VENT the system, the PCM has to make up for that added air by adding fuel via LTFT.
If you examine them, they will most likely be POSITIVE (shoule be near zero to slight negative)
Still, that would be a BOTH BANK issue. SO, take a look at SPARY and FUEL and all the things that make it happen for that bank.
Bill
So, when you have a vacuum leak or the PCV leaks or you just VENT the system, the PCM has to make up for that added air by adding fuel via LTFT.
If you examine them, they will most likely be POSITIVE (shoule be near zero to slight negative)
Still, that would be a BOTH BANK issue. SO, take a look at SPARY and FUEL and all the things that make it happen for that bank.
Bill
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Do you have an owners manual for that scanner. Read it. 
The EVAP means the emissions status for the fuel tank is not ready.
Not sure what the others in red mean without guessing
AIR could mean that the Air Injection Reaction (A.I.R. System) is not ready.
The EVAP means the emissions status for the fuel tank is not ready.
Not sure what the others in red mean without guessing
AIR could mean that the Air Injection Reaction (A.I.R. System) is not ready.